text: * 1801 – Jean-Baptiste Lamarck began the detailed study of invertebrate taxonomy.
  * 1802 – The term biology in its modern sense was propounded independently by Gottfried Reinhold Treviranus (Biologie oder Philosophie der lebenden Natur) and Lamarck (Hydrogéologie). The word was coined in 1800 by Karl Friedrich Burdach.
  * 1809 – Lamarck proposed a modern theory of evolution based on the inheritance of acquired characteristics.
  * 1817 – Pierre-Joseph Pelletier and Joseph Bienaimé Caventou isolated chlorophyll.
  * 1820 – Christian Friedrich Nasse formulated Nasse's law: hemophilia occurs only in males and is passed on by unaffected females.
  * 1824 – J. L. Prevost and J. B. Dumas showed that the sperm in semen were not parasites, as previously thought, but, instead, the agents of fertilization.
  * 1826 – Karl von Baer showed that the eggs of mammals are in the ovaries, ending a 200-year search for the mammalian egg.
  * 1828 – Friedrich Woehler synthesized urea; first synthesis of an organic compound from inorganic starting materials.
  * 1836 – Theodor Schwann discovered pepsin in extracts from the stomach lining; first isolation of an animal enzyme.
  * 1837 – Theodor Schwann showed that heating air will prevent it from causing putrefaction.
  * 1838 – Matthias Schleiden proposed that all plants are composed of cells.
  * 1839 – Theodor Schwann proposed that all animal tissues are composed of cells. Schwann and Schleinden argued that cells are the elementary particles of life.
  * 1843 – Martin Barry reported the fusion of a sperm and an egg for rabbits in a 1-page paper in the Philosophical Transactions of the Royal Society of London.
  * 1856 – Louis Pasteur stated that microorganisms produce fermentation.
  * 1858 – Charles R. Darwin and Alfred Wallace independently proposed a theory of biological evolution ("descent through modification") by means of natural selection.  Only in later editions of his works did Darwin used the term "evolution."
  * 1858 – Rudolf Virchow proposed that cells can only arise from pre-existing cells; "Omnis cellula e celulla," all cell from cells. The Cell Theory states that all organisms are composed of cells (Schleiden and Schwann), and cells can only come from other cells (Virchow).
  * 1864 – Louis Pasteur disproved the spontaneous generation of cellular life.
  * 1865 – Gregor Mendel demonstrated in pea plants that inheritance follows definite rules. The Principle of Segregation states that each organism has two genes per trait, which segregate when the organism makes eggs or sperm. The Principle of Independent Assortment states that each gene in a pair is distributed independently during the formation of eggs or sperm. Mendel's trailblazing foundation for the science of genetics went unnoticed, to his lasting disappointment.
  * 1865 – Friedrich August Kekulé von Stradonitz realized that benzene is composed of carbon and hydrogen atoms in a hexagonal ring.
  * 1869 – Friedrich Miescher discovered nucleic acids in the nuclei of cells.
  * 1874 – Jacobus van 't Hoff and Joseph-Achille Le Bel advanced a three-dimensional stereochemical representation of organic molecules and propose a tetrahedral carbon atom.
  * 1876 – Oskar Hertwig and Hermann Fol independently described (in sea urchin eggs) the entry of sperm into the egg and the subsequent fusion of the egg and sperm nuclei to form a single new nucleus.
  * 1884 – Emil Fischer began his detailed analysis of the compositions and structures of sugars.
  * 1892 – Hans Driesch separated the individual cells of a 2-cell sea urchin embryo and shows that each cell develops into a complete individual, thus disproving the theory of preformation and showing that each cell is "totipotent," containing all the hereditary information necessary to form an individual.
  * 1898 – Martinus Beijerinck used filtering experiments to show that tobacco mosaic disease is caused by something smaller than a bacterium, which he names a virus.